On Tue, Sep 14, 2021 at 09:13:48AM +0200, Michal Hocko <mhocko@xxxxxxxx> wrote: > " > This object can consume up to 2 pages, syscall is sleeping one, > size and duration can be controlled by user, and this allocation > can be repeated by many thread at the same time. > " > > It sounds like a problem, except it is not because? A worst case > scenario evaluation would be beneficial for example AFAICS, the offending allocation is in place only during the duration of the syscall. So it's basically O(#tasks). Considering at least 2 pages for task_struct + 2 pages for kernel stack, back of the envelope calculation gives me the footprint amplification is <1.5. The factor would IMO be interesting if it was >> 2 (from the PoV of excessive (ab)use, fine-grained accounting seems to be currently unfeasible due to performance impact). The commit message can be more explicit about this but to the patch Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx>
